In the field of wireless communication, especially in mobile communication, a variety of information such as image and data in addition to voice is becoming an object of transmission in recent years. It is anticipated that the demand for high-speed transmission becomes further increased in the future, and to perform high-speed transmission, a wireless transmission scheme, which utilizes limited frequency resources more effectively and achieves high transmission efficiency, has been required.
OFDM (Orthogonal Frequency Division Multiplexing) is one of wireless transmission techniques, for meeting these requirements. OFDM is one of multicarrier communication techniques, whereby data is transmitted in parallel using a large number of subcarriers, and it is known that OFDM provides high frequency use efficiency and reduce inter-symbol interference under a multipath environment and is effective to improve transmission efficiency.
Moreover, in OFDM, cases occur where quality varies significantly per subcarrier due to frequency selective fading caused by multipath. In this case, signals allocated to subcarriers located in a fading valley shows poorer quality and are difficult to demodulate, so that it is necessary to improve quality so as to enable demodulation.
Repetition technique is one of techniques to improve quality in OFDM. The repetition technique refers to a technique of creating a plurality of the same symbols by duplicating (repeating) a given symbol, and allocating and transmitting the plurality of the same symbols to different subcarriers or at different timings. A receiving side acquires diversity gain by maximum-ratio-combination of those of the same symbols (see, for example, Non-patent Document 1).    Non-patent Document 1: “Performance Comparions between OFCDM and OFDM in a Forward Link Broadband Channel”, Maeda, Atarashi, Kishiyama, and Sawahashi, Technical report of IEICE., RCS2002-162, August 2002.